An inborn defect in the metabolism of tyrosine in infants on a normal diet

Abstract

Fourteen infants, out of 1276 tested, were found to excrete large amounts of p-hydroxyphenylpyruvic acid, p-hydroxyphenyl-lactic acid and tyrosine. p-Hydroxyphenylacetic acid was present in the urine but may be an artifact. Tyrosine O-sulphate was not detected. A variable proportion of the tyrosine was conjugated as a low-molecular-weight compound with basic properties. In contrast with previous reports of hydroxy-phenyluria, these infants were fed on a normal diet with only a moderate protein intake and (in 7 cases) supplementary ascorbic acid. They were well, with no evidence of liver dysfunction. Some were premature and some full-term, and they were aged up to 68 days. The hydroxy-phenyluria ceased abruptly after a time without any treatment. It is suggested that these infants lacked an enzyme concerned with oxidizing p-hydroxyphenylpyruvic acid to homogentisic acid and that the ability to carry out this reaction first appears at different absolute ages in different individuals.